In the past, paper-based flow sheets, located at a patient's bedside, were typically used in hospitals to store medical data concerning that patient. This method was time-consuming and costly.
More recently, hospitals have turned to computer technology to store and view patient information at the patient's bedside. An example of such a system is the Carevue 900 system, manufactured and sold by Hewlett-Packard Company, Clinical Information Systems. These systems chronologically display on a computer screen a predetermined set of trend data that are derived from data that are sensed by transducers attached to the patient. A typical display is shown in FIG. 1.
In these systems, the clinician is forced to scan the information in a basically sequential fashion. Moreover, the displayed information is typically limited to directly measurable physical quantities or trend data derived therefrom. Sequential scanning is time consuming, and the displayed information can be over- or under-informative from the perspective of the clinician.
Clinicians, when analyzing a patient, are generally interested in "events." Events are constructs involving relationships among different measurements. For example, an event can be a particular measurement occurring at a particular rate, or attaining a particular threshold. In addition, an event can be the concurrence of several measurements attaining particular thresholds or occurring at particular rates.
For example, hypothermia is a condition of abnormally low body temperature. This condition can be serious if it lasts for an extended period. Thus, a clinician may wish to detect if the patient's body temperature was below 92.degree. F. for a duration greater than one hour. In addition, symptomatic tachychardia is a condition in which the heart rate is very fast and the resulting blood pressure drops below a certain level. Thus, a clinician may wish to detect when the patient's heart rate was greater than 180 beats per minute for a duration greater than 30 seconds and detect whether the patient's systolic arterial blood pressure was less than 80 mmHg for a duration greater than 30 seconds.
If they had their choice, clinicians would prefer to directly view event occurrences on the computer screen. Moreover, they would prefer to tailor event definitions on a per-patient basis, and they would prefer the ability to scan through events and data related to those events in a random as well as a sequential manner. Clinicians also prefer the ability to tailor the list of displayed events.